For years I have been running Windows only when I absolutely need to via Virtualbox on a Linux (Mint 20.2) host. VBox requires that you use the 32 bit Windows versions. After a recent Linux system upgrade from 17.3 I had to reinstall most of my software. This included VirtualBox and Windows. Then I had to reinstall B4A along with the needed files: net, jdk & sdk. Maybe there was something wrong with all of this, although, as I said, B4A appears to be working fine, that is until I try to compile.